The invention relates to a door handle arrangement for vehicles. In particular, the invention relates to a door handle arrangement for vehicles which uses a capacitive touch sensor which is actuated by application of pressure to an actuating surface.
Pressure-sensitive capacitive detection devices are known in the prior art. For example, WO 2011/130755 A2 discloses a capacitive detection device. In this detection device, a sensor surface is brought into the vicinity of a metal cover. By pressing on the metal cover the distance between cover and sensor surface can be varied and the variable capacitance is detected.
The document US 2012/0326566 A1 also discloses a capacitive sensor. An excitation electrode is disposed above a fixed electrode and an oscillating circuit is connected to the capacitance thus formed. The detuning of the oscillating circuit is detected as a measure for the change in the capacitance.
In motor vehicles, capacitive sensors for detecting user actuations are primarily known as proximity sensors which detect a mere approach of a body part of a user into the proximity of the sensor. Contact is not necessary with these sensors. For example, such capacitive proximity sensors are disposed in the door handles of vehicles in order to sense the approach of a user for so-called keyless entry systems. The approaching user changes the environment (the surrounding dielectric) of an electrode disposed in the door handle and thus changes the capacitance between this electrode and a reference. In addition, the capacitance of the user himself has effects on the capacitance system of the sensor being studied.
Touch sensors which respond to buttons or pressure are frequently realized by means of mechanical contact switches in vehicles.
One problem with capacitive proximity sensors is that environmental influences significantly affect the sensitivity of the arrangement and also erroneous detections. Other environmental influences such as snow, rain or air humidity lead to erroneous detections. In addition, the external shape of the vehicle cannot be selected arbitrarily in the sensor area. In particular, coatings, e.g. chrome parts inhibit sensing in the outer area if the sensing electrode area is substantially covered by a metal layer. Mechanical contact switches in turn perturb the appearance and are expensive to seal to keep environmental influences away from the interior of a vehicle handle.